2, 3, 6-trichloro-5-nitrobenzoic acid herbicidal use



United States Patent 3,248,208 2,3,\E-TRICHLORO-S-NITROBENZOIC ACID HERBICIDAL USE Edward ll). Weil, Lewiston, N.Y., assignor to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Filed Nov. 29, 1962, Ser. No. 241,063 2 Claims. (Cl. 71-245) This invention relates to a composition of matter known as a ring chlorinated and nitrated benzoic acid.

This is a continuation-in-part of my co-pending application Serial No. 740,992, filed June 10, 1958, now United States Patent 3,109,023.

The present invention is of a position isomer of the above-mentioned class of substances, identified by its molecular structure as 2,3,6-trichloro-S-nitrobenzoic acid.

Such a product and its described derivatives have special 7 properties as selective herbicides, not logically predictable from the established herbicidal properties of other known isomers in their class.

The substance can be prepared in the following manner:

Seventy-five grams of 2,3,6-trichlorobenzoic acid was refluxed for twelve hours with two hundred and fifty milliliters of red fuming nitric acid. The reaction mixture Was then poured into one thousand milliliters of water, cooled to 0-5 degrees centigrade, filtered, and the solids washed with a small amount of water, then dried in air. The product comprises seventy-five grams of pale yellow crystalline solid, melting at 156.5-157 degrees centigrade. After recrystallization from benZene-heptane the product melted at one hundred and fifty-seven degrees centigrade.

Analysis.Calculated for C7H2C13NO4: N, 5.17. Found: N, 5.1.

The structure of the product was proved by decarboxylation to 1,2,4-trich1or0-S-nitrobenzene, melting point fifty-seven to fifty-eight degrees centigrade.

It is important in agricultural practice to use a plant growth regulator which will control weeds but which will have little or no adverse effect on the crops in the treated area. The benzoic acids and related compounds that have heretofore been used have not generally exhibited this selectivity on most crops. In particular, the hitherto known benzoic herbicides cannot be used to control weeds in dicotyledonous crops because of their serious damaging effect on said crops.

The compounds of this invention were found to have good herbicidal action on broadleaf weeds but produced no damaging effect on desirable grasses or soybeans. This is in contrast to the un-nitrated active tri and tetrachlorobenzoic acids which are quite damaging to most grasses and to soybeans. It was completely unexpected and, therefore, could not have been predicted that 2,3,6-trichloro-S-nitrobenzoic acid would have these unusual selective properties. Further surprising was the fact that the prior art indicated that some chloronitrobenzoic acids do not even have plant growth regulating properties.

An area of sandy loam soil naturally infested with lambsquarters, ragweed, burdock, smartweed, and pigweed were plowed, disked and planted with sweet corn, soybeans, and millet. Separate plots were then sprayed with an emulsifiable oil formulation of 2,3,6-trichloro-5- nitrobenzoic acid and a commercial polychlorobenzoic acid herbicide consisting of approximately nineteen percent 2,3,6-trichlorobenzoic acid, fifty-two percent 2,3,5- trichlorobenzoic acid, eight percent 2,3,5,6-tetra-chlorobenzoic acid, and twenty-one percent inert ingredients. Both compositions were applied at the rate of eight pounds per acre. A control plot was left unsprayed.

The plots were inspected after seven weeks. The unsprayed plot was heavily overgrown with broadleaf weeds,

the plot treated with the commercial polychlorobenzoic acid herbicide exhibited excellent broadleaf weed control but the millet and soybeans were killed and the corn was severely injured (severe stunting and deformation). Even by reducing the rate of application to one pound per acre, the polychlorobenzoic acid still severely injured soybeans. The plot treated with 2,3,6-triehloro-S-nitroben- Zoic acid exhibited excellent broadleaf Weed control, but the corn, millet and soybeans were undamaged.

Derivatives of the acid of this invention may be advantageous for certain uses and if desired the ester and amide may be used. Such derivatives are prepared by reacting the free acid, or acid chloride, with alcohols or amines in the conventional manner for conducting esterification or amidation processes.

The compound of the invention can also be used for other purposes, for example, as a chemical intermediate. Reduction of the compounds depending on conditions, yields the corresponding S-amino, 5-hydroxylamino-, 5,5- azo-, or 5,5-azoxy substituted 2,3,6-trichlorobenzoic acids, which are also useful plant growth regulators.

In determining whether it is advantageous to use in the field any of the aforementioned derivatives or salts of the 2,3,6-trichloro-S-nitrobenzoic acid rather than the acid per se, one determines the field conditions and selects the particular derivative or salt having the required characteristics to meet such conditions.

The compound of this invention may be used with any conventional diluent such as clay, wood flour, Fullers earth, soybean flour, or any liquid carrier such as xylene, kerosene, alcohols and ketones or other carriers may be used, depending on the economics and distribution requirements. Formulations may contain emulsifying agents, such as sorbitol, polyoxyethylene ethers and sodium alkyl sulfate, and carriers in accordance with the well-established practices in the herbicidal field.

Examples of formulations that may be used are as follows:

Example 1 Ten parts of 2,3,6-trichloro-5-nitrobenzoic acid and five parts of a commercial polyoxyethylene ether emulsifier were dissolved in thirty parts of Xylene to obtain a solution emulsifiable with water.

Example 2 One part of 2,3,6-trichloro-5-nitrobenzoic acid was agitated with fifty parts of Water and four percent solution of sodium hydroxide was added until a pH of eight to nine was reached. The solution was then diluted with water to make one hundred parts of a one percent solution of the sodium salt of 2,3,6-trichloro-S-nitrobenzoic acid. This could be sprayed as such or further diluted with water to make a spray solution.

Other water-soluble salts such as the potassium salt, ammonium salt and the mono-, di-, or trialkylammonium salts may be similarly formulated and used.

Suitable salts include those which contain an inorganic or organic cation such as sodium, potassium, calcium, strontium, barium, magnesium, aluminum, iron, cobalt, nickel, zinc, cadmium, mercury, copper, ammonium, mono-, diand tri-hydrocarbyl-substituted ammonium, mono-, diand tri-alkanolammonium, and mixed alkylalkanolammonium in chemical combination with such number of 2,3,6-trichloro-S-nitrobenzoate anion or anions as is demanded to satisfy valence requirements.

The alkylammonium salts such as monoalkylammonium, dialkylammonium, or trialkylammonium preferably have from 1 to 18 carbon atoms in each alkyl group, the total number of carbon atoms preferably being not more than 18. The alkanolammonium salts such as monoalkanolarnmonium, dialkanolammonium, or trialkanolammonium preferably have from 2 to 3 carbon atoms in each alkanol group. The mixed alkylalkanolammonium salts such as monoalkyl monoalkanolammonium, dialkyl monoalkanolammonium, or monoalkyl dialkanolammonium preferably have from 1 to 4 carbon atoms in each alkyl group and from 2 to 3 carbon atoms in each alkanol group.

Examples of monoalkylammonium salts are the monomethylammonium, monoethylammonium, monopropylammonium, monobutylammonium, monoarnylammonium, monohexylarnmonium, monoheptylammonium, monooctylammonium, monononylammonium, monodecylammonium, monoundecylammonium, monododecylammonium, and similar moonalkylammonium salts of 2,3,6-trichloro-5-nitrobenzoic acid.

Examples of dialkylammoniurn salts are the dimethylammonium, diethylammonium, dipropylammonium, dibutylammonium, diamylammonium, dihexylammonium, methylethylammonium, ethylpropylammonium, propylbutylammonium, butylamylammonium, amylhexylammonium, methylundecylammonium, and similar dialkylammonium salts of 2,3,6-trichloro-5-benzoic acid.

Examples of trialkylammonium salts are the trimethylammonium, triethylammonium, tripropylammonium, tributylammonium, methyldiethylammonium, ethyldipropylammonium, propyldibutylammonium, methyldiamylarnmonium, ethyldiamylammonium, methylethylpropylammonium, etbylpropylbutylarnmonium, dimethyllaurylammonium, dimethylstearylammonium and similar salts of 2,3,6-trichloro-S-nitrobenzoic acid.

Examples of monoalkanolammonium salts are the monoethanolammonium, monopropanolammonium, and similar salts of 2,3,6-trichloro-5-benzoic acid.

Examples of dialkanolammonium salts are the diethanolammonium, dipropanolammonium, ethanolpropanolammonium and similar salts of 2,3,6-trichloro-5- nitrobenzoic acid.

Examples of trialkanolammonium salts are the triethanolammonium, tripropanolammonium, ethanoldipropanolammonium, propanoldiethanolammonium, and similar salts of 2,3,6-trichloro-S-nitrobenzoic acid.

Examples of monoalkyl monoalkanolammonium salts are the methylethanolammonium, ethylethanolammoniurn, propylethanolammonium, butylethanolammonium, methylpropanolammonium, ethylpropanolarnmonium, propylpropanolammonium, butylpropanolammonium, and similar salts of 2,3,6-trichloro-S-uitrobenzoic acid.

Examples of dialkyl monoalkanolammonium salts are the climethylethanolammonium, diethylethanolammonium, dipropylethanolammonium, dibutylethanolammonium, dimethylpropanolammonium, diethylpropanolammonium, dipropylpropanolammonium, dibutylpropanolammonium, methylethylethanolammonium, methylethylpropanolammonium, ethylpropylethanolammonium, ethylpropylpropanolammonium, propylbutylethanolammonium, propylbutylpropanolammonium, and similar salts of 2,3,6-trichloro-S-nitrobenzoic acid.

Examples of monoalkyl dialkanolammonium salts are the methyldiethanolammonium, ethyldiethanolammonium, propyldiethanolammonium, butyldiethanolammoniurn, methyldipropanolammonium, ethyldipropanolammonium, propyldipropanolammonium, butyldipropanolammonium, methylethanolpropanolammonium, ethylethanolpropanolammonium, propylethanolpropanolammonium, butylethanolpropanolammonium, and similar salts of 2,3,6-trichloro-5-nitrobenzoic acid.

Examples of dialkylammonium salts in which the radicats are conjoined to form a ring are piperidinium, pyrolidinium, and morpholinium salts. Examples of trialkylammonium salts in which the radicals are conjoined to form a ring are N-methylmorpholinium salts. Examples of alkylammonium salts in which the alkyl groups are cycloaliphatic include cyclohexylammonium and dicyclohexylammonium salts of 2,3,6-trichloro-5-nitr0benzoic acid.

Examples of hydrocarbylammonium salts in which the hydrocarbyl radical is aromatic include the anilinium, N-methylanilinium, N,N-dimethylanilinium, naphthylammonium, and benzylammonium salts.

Example 3 A solution of 30 percent dimethylamine in water was added to a stirred mixture of 10 parts of 2,3,6-trichloro- S-nitrobenzoic acid and parts of water until a pH of 8.5 was reached. There was obtained a clear solution of the dimcthylammonium salt of 2,3,6-trichloro-5-nitrobenzoic acid, which was suitable for hydrogenation over 5 percent platinum on charcoal catalyst to the dimethylammonium salt of 2,3,6-trichloro-S-aminobenzoic acid.

Example 4 To 27 parts of 2,3,6-trichloro-5-nitrobenzoic acid in 200 parts of alcohol were added 10 parts of triethylamine. The mixture was then evaporated to dryness to obtain the triethylammonium salt of 2,3,6-trichloro-5-nitrobenzoic acid as a water-soluble neutral solid. The solution when sprayed on soil at 6 pounds of salt per acre, prevented the germination and growth of ragweed, pigweed, and lambsquarters.

Example 5 To 54 parts of 2,3,6-trichloro-S-nitrobenzoic acid in 250 parts of ethyl alcohol was added 21 parts of diethanolamine. The neutral solution was evaporated to obtain a water immiscible syrup. This salt was dilutable with water to form clear solutions which, when sprayed on turf at 20 pounds of salt per acre, prevented crabgrass germination with negligible turf injury.

Example 6 The anilinium salt of 2,3,6-trichloro-S-nitrobenzoic acid precipitated as a solid upon admixture of 50 cc. of 0.1-N 2,3,6-trichloro-S-nitrobenzoic acid in ethyl ether with 50 cc. of 0.1-N anilinium salt in ether, and could be removed and isolated in substantially quantitative yield by filtration.

Example 7 One mole of dimethyllaurylamine was heated at 100 degrees centigrade with one mole of 2,3,6-trichloro-5- nitrobenzoic acid until the mixture fused to a homogeneous mass. This salt was soluble in heavy aromatic naphtha. Solutions at 5 percent in this solvent were phytotoxic to plantain, dandelion, goldenrod, and chicory.

Combinations of this herbicide with other known herbicides or compositions for controlling the growth of vegetation and plants to obtain desirable combinations and properties are within the spirit of this invention. The compounds of this invention can be advantageously used in mixtures with other compounds capable of producing desirable rapid destruction of plants or vegetation.

For example, 2,3,6-trichloro-S-nitrobenzoic acid or its soluble salts can advantageously be used in conjunction with 2,4-dichlorophenoxyacetic acid, or salts thereof, 4-chloro-2-methylphenoxyacetic acid or salt thereof, N,N-diallyl-2-chloroacetamide, N,N-diethyl-2-chloroacetamide, ethyl N,N-di-n-propylthiolcarbamate, 2-chloroallyl diethyldithiocarbamate, and others. This list is intended to be representative, and it is understood that other reasonable combinations may be used. The examples and methods of preparation disclosed have been given for purposes of illustration only and do not restrict the invention to the specifics herein illustrated. Many other modifications and ramifications will naturally suggest themselves to those skilled in the art, based on the disclosure of the basic discovery. These are intended to be comprehended within the scope of my invention.

I claim: References Cited by the Examiner 1. A method of regulating plant growth which com- UNITED STATES PATENTS prises applying to the media to be treated a phytotoxu: amount of a composition having as an active ingredient 23,94,916 2/1946 101165 a compound selected from the group consisting of 2,3,6- 5 3,005,694 10/1961 Entemann 71-2.6 trichloro-5-nitrobenzoic acid and its water soluble salts. 3,009,806 11/1961 Weil et al 71-26 2. A method of regulating plant growth which com- 3 013 73 12 19 1 Hart et 1 71 2 6 prises applying to the media to be treated a phytotoxic amount of a compound selected from the group con- LEWIS GOTTS, Primary Examiner sisting of 2,3,6-trichloro-5-nitr0benzoic acid and its water 10 soluble salts together with a carrier. JULIAN S. LEVITT, Examiner. 

1. A METHOD OF REGULATING PLANT GROWTH WHICH COMPRISES APPLYING TO THE MEDIA TO BE TREATED A PHYTOTOXIC AMOUNT OF A COMPOSITION HAVING AS AN ACTIVE INGREDIENT A COMPOUND SELECTED FROM THE GROUP CONSISTING OF 2,3,6TRICHLORO-5-NITROBENZOIC ACID AND ITS WATER SOLUBLE SALTS. 